<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
    <button id="button">按钮</button>
    <script>
        var xu=document.getElementById("button");
        xu.addEventListener("click",hello);
        xu.addEventListener("click",nihao);
        xu.removeEventListener("click",hello);
        xu.removeEventListener("click",nihao);

        function hello(){
            alert("hello");
        }
        function nihao(){
            alert("nihao");
        }
    </script>
</body>
</html>